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Date: 29 Sep 92 17:07:54 GMT
From: wdl39!mab@ford-wdl1.arpa  (Mark A Biggar)
Subject: Re: Declaring Arrays of Bits (how)?
Message-ID: <1992Sep29.170754.4140@wdl.loral.com>
List-Id: <comp.lang.ada>

In article <YOUNG.92Sep29101112@kuwait.gdfwc3> young@gdfwc3 (Mark Young) writes
:
>I am trying to declare arrays of bits in Ada.  Here's my attempt:
>type Array_Range_Type is range 1..128;
>type Bit_Type is (OFF, ON);
>for  Bit_Type use (OFF => 0, ON => 1);
>for  Bit_Type'size use 1;
>type Bit_Array_Type is array (Array_Range_Type) of Bit_Type;
>Bit_Array : Bit_Array_Type;
>
>This looks right to me.  I would expect Bit_Array to be represented
>as an array of 128 bits (128 contiguous bits).  This is not the case,
>however.  My compiler (XDADA) is representing Bit_Array as an array
>of 128 bytes.  As an added note, I have been using representation clauses
>for records without any problems.  
>Am I missing something?  
>Is there a special representation clause for arrays that I am overlooking? 
>Is my compiler at fault?

For most compilers you probably need to throw a:

pragma PACKED(Bit_Array_Type);

in the mix somewhere as well.  Otherwise according to the LRM the compiler is
under no obligation to put the array element in anything smaller then a byte
each unless you add the pragma PACKED.

--
Mark Biggar
mab@wdl1.wdl.loral.com